Laminated pressure vessels



T. J. RElNHART, JR

Filed Dec. 4, 1962 LAMINATED PRESSURE VESSELS Sept. 21, 1965 li'lln"United States Patent O 3,207,352 LAMINATED PRESSURE VESSELS Theodore J.Reinhart, Jr., 4116 Woodedge Drive, Bellbrook, Ohio Filed Dec.. 4, 1962,Ser. No. 242,335 4 Claims. (Cl. 220-3) The .invention described hereinmay be manufactured and used by or for the Government for governmentalpurposes without the payment to me of any royalty thereon.

This invention relates generally to pressure vessels and, morespecifically, to laminated pressure vessels under extremely highpressure. Futhermore, pressure vessels in accordance with this inventionmay be either so-called closed vessels or open vessels such as rocketmotor cases.

It has been well established that when the wall thickness .of a pressurevessel approaches of its radius, the thin wall pressure vessel formulasand membrane theory .are no longer applicable. r[Thick-wall theory mustbe applied in the design of such vessels and structures.

It is well known that when a thick wall pressure vessel is internallypressurized, a stress gradient is set up in the Wall. The inducedtensile .stresses are a maximum at the inside radius and diminish towardthe outside radius. Likewise, when such a pressure vessel is subjectedto external pressure, the compressive stresses progressively increasefrom the outer t-o the inner radius of the vessel.

In the conventional thick-wall homogeneous or laminated vessels, thisstress gradient has been ignored and the vessels designed t-o limit themaximum stress to that which the inner layer of material may withstand.This, by necessity, results in a relatively inefficient use of materialand .a heavy vessel. Not only are needlessly heavy pressure vessels moreexpensive to fabricate, but in many applications .such as found onairplanes and space craft, such excess weight is extremely detrimental.

This invention provides a simple and effective solution to thethick-wall, stress gradient problem. yPressure vessels made inaccordance with this invention consist of lament or tape woundcontiguous or laminated shells, being of so-called thinlayerconstruction, each shell from the inner to the outer being formed of amaterial having a greater modulus of elasticity than the precedingshell. The actual dimensional design of the pressure vessel may be bytrial and error or in accordance with formula-s developed for variousshaped ves-sels.

When a pressure vessel made in accordance with this invention ispressurized, the greater .stiffness of the outer layer causes it toabsorb stress at a greater rate than its immediately adjacent innershell. IFurthermore, the greater stiffness of the outer layers tend torestrict the stress absorption of the inner layers. The inter-shellinteraction, bein-g in direct opposition to the stress gradient of athick wall structure, tends to counteract or negate the stress gradientin the conventional thick wall vessel.

When a pressure vessel made in accordance with this invention issubjected to external pressure, as when used at depths in the ocean, theinteraction between shells would, in like manner, serve to level out thecompressive stress gradient induced in the wall of the vessel.

A vessel made in accordance with this invention, by the proper selectionof materials and shell thickness, may be made to have a wall having asubstantially uniform stress level throughout. Such a vessel may be madewith the minimum .amount of material working at maximum efficiency.

The primary object of this invention is to provide a pressure vessel inwhich all the material comprising the walls is substantially stressed.

Another object of this invention is to provide a laminated pressurevessel corresponding to a conventional thick-wall vessel and in whicheach shell is carrying a proportion-ate part of the stress resultingfrom the pressure acting on the vessel.

A further object of this invention is to provide a laminated pressurevessel `in which the various shells may be made of materials each havinga ditferent modulus of elasticity in order to secure better stressdistribution within the Walls of the vessel.

Yet another object of this invention is to provide the lightest possiblehigh pressure vessel, by efficiently utilizing the .materials comprisingthe vessel.

A still further object of this invention is to provide a high strength,lightweight pressure vessel lhaving a plurality of laminated orcontiguous shells which are seamless and in which the materialscomprising the walls are substantially and more or less uniformlystressed from either internal or external pressure.

Additional objects, advantages .and features of the invention reside inthe construction, arrangement and combination of parts involved in theembodiments of the invention las will appear from the followingdescription and accompanying drawings, wherein:

FIG. 1 shows a spherical vessel in partial section as representa-tive ofa closed pressure vessel made in accordance with this invention,

FIG. 2 shows in partial section an open end vessel such as used onrocket mot-ors, as representative of open end pressure vessels made inaccordance with the invention, and

FIG. 3 is ran enlarged fragmentary sectional view showing the wallconstruction details of the spherical vessel of FIG. 1; the constructiondetails being equally applicable to the vessel shown on FIG. 2.

Referring to FIG. l, which is represent-ative of closed Vesselstructures, the pressure vessel referred to generally as vessel 10 isshown as having three contiguous shells: the outer shell 12, theintermediate shell 14 and the inner shell 16. Although three shells areshown, any number of shells greater than one m-ay be used within thescope of the invention. Each shell may be made of any suitable materialin the form of lilaments or tapes and wound in a manner well known tothe art. Suitable bonding materials may be used during construction, andthe vessel so formed may be cured as dictated; the bonding and curingprocesses being well known t-o the art and not constituting par-t ofthis invention.

If desired, a strain-absorbing elastomeric coating 18 and 18a may beapplied between shells. Such coating may be made of butyl rubber, forexample. Such coating has little compressibility and serves to absorbstrain differentials between the shells.

In many applicati-ons, depending upon .the .gases to be contained withinthe vessel, and permeability of the vessel, the vessel so formed will becompletely satisfactory. In other applications, it may be desirable oreven necessary to use an inner liner 20 which may be metallic or of lowpermeable non-metallic material. If desired, the completed vessel may becoated with a moisture barrier or protective coating 22.

The vessel is provided with suitable connective openings such as opening24. Such openings, which are usually threaded or anged, are not claimedas part of this invention and may .be built into the vessel in mannerswell known t-o the art.

The tabulation below, which in no Way limits the materials which may beused in the construction of vessels in accordance with this invention,is intended to show how materials for the various shells may be selectedbased upon a graduated modulus of elasticity. Likewise, there is nolimitation stating that all shells should be constructed from materialsin the same group. For example, a vessel could readily be made havingone shell of glass filaments, one of metal filaments and one of organicfilaments.

Glass filaments Designation: Elastic modulus, p.s.i. E glass 10.5 106994 glass 12.5Xl(i YM31A glass 16.0 106 Metal larnents Elastic modulus,p.s.i. Titanium l7 l0s steel 3o 10fi Molybdenum 50 l06 Organic filamentsElastic modulus, grams/ denier Nylon 60 Daeron 80 Fortisan 100 Ht-l 140A second embodiment of the invention is shown on FIG. 2 which isrepresentative of open pressure vessels such as used for example on amissile motor case. The

vessel depicted by FIG. 2 may be made in accordancewith the method usedin making the closed pressure vessel previously described. Accordingly,like elements on both figures are designated by like numerals.

Pressure vessels in accordance with this invention may be made bywinding onto a suitable mandrel. With vessels which do not use ametallic inner liner, such a mandrel may be cast or otherwise formed oflow melting temperature metals or alloys, as for example Woods metal.After the vessel is completed, the metal is melted and poured from thevessel through one of the openings.

With Vessels using a metallic inner liner, the mandrel may be formed byfilling the liner with a liquid low melting temperature metal or alloywhich is then allowed to solidify. After the vessel is formed, the metalis again liquefied and poured from the Vessel.

It is to be understood that the embodiments of the present invention asshown and described are to be regarded as illustrative only and that theinvention is susceptible to variations, modifications and changes withinthe scope of the appended claims.

I claim:

1. A laminated pressure Vessel comprising: at least three contiguousshells, each shell being of continuous filament Wound multilayerconstruction from a continuous filament supply and each shell from theinside out being of a filament having a higher modulus of elasticitythan the filament forming the preceding shell.

2. A laminated pressure vessel comprising: at least three contiguousshells and a metallic inner liner having its outer surface joined to theinside surface of the innermost shell, each shell being of continuousfilament wound multilayer construction from a continuous filament supplyand each shell from the inside out being of a filament having a highermodulus of elasticity than the filament forming the preceding shell.

3. A laminated pressure vessel comprising: at least three contiguousshells and an elastomeric stress distributing coating between eachshell, each shell being of continuous filament Wound multilayerconstruction from a continuous filament supply and each shell from theinside out being of a filament having a higher modulus of elasticitythan the filament forming the preceding shell,

4. A laminated pressure vessel comprising: at least three contiguousshells, an elastomeric stress distributing coating between each shell,and a metallic inner liner having its outer surface joined to the insidesurface of the innermost shell, each shell being of continuous filamentwound multilayer construction from a continuous filament supply and eachshell from the inside out being of a filament having a higher modulus ofelasticity than the filament forming the preceding shell.

References Cited by the Examiner UNITED STATES PATENTS 2,652,943 9/53Williams 220-3 2,744,043 5/56 Ramberg 156-155 2,786,007 3/57 Chew156-155 2,809,762 10/57 Cardona 220-63 2,988,240 6/61 Hardesty 220-33,023,495 3/62 Noland 220-3 3,031,099 4/62 Wiltshire 220-3 3,047,1917/62 Young 220-3 THERON E. CONDON, Primary Examiner.

EARLE I. DRUMMOND, Examiner.

4. A LAMINATED PRESSURE VESSEL COMPRISING: AT LEAST THREE CONTIGUOUSSHELLS, AN ELASTOMERTIC STRESS DISTRIBUTING COATING BETWEEN EACH SHELL,AND A METALLIC INNER LINER HAVING ITS OUTER SURFACE JOINED TO THE INSIDESURFACE OF THE INNERMOST SHELL, EACH SHELL BEING OF CONTINUOUS FILAMENTWOUND MULTILAYER CONSTRUCTION FROM A CONTINUOUS FILAMENT SUPPLY AND EACHSHELL FROM THE INSIDE OUT BEING OF A FILAMENT HAVING A HIGHER MODULUS OFELASTICITY THAN THE FILAMENT FORMING THE PRECEDING SHELL.